摘要Background:The golden Syrian hamster is a valuable animal model for studying car-cinogenesis,metabolic disorders,cardiovascular diseases,and viral infections due to its biological and pathological similarities to humans.However,the development of ge-netically engineered hamsters has lagged behind that of mice and rats,largely because of an embryonic development block at the two-cell stage in vitro.Although CRISPR/Cas9-mediated gene knockout has been achieved in hamsters,precise DNA fragment insertion or conditional knockout(cKO)models have not previously been reported,likely due to technical limitations in embryo manipulation and insufficient efficiency of homology-directed repair(HDR).Methods:In this study,we generated conditional alleles of the ApoF gene in golden Syrian hamsters.A two-cut strategy was applied using Cas9 protein,two sgRNAs,and a single donor plasmid containing exon 2 flanked by loxP sites and two～0.8 kb homol-ogy arms.A mixture of Cas9 protein,sgRNAs,and the donor plasmid was microin-jected into the pronuclei of one-cell stage hamster embryos.Results:The efficiency of CRISPR/Cas9-mediated loxP knock-in reached up to 27％,and the genetically modified floxed alleles were successfully transmitted through the germline.The functionality of the inserted loxP sites was validated by in vivo Cre-mediated recombination following local administration of AAV vectors,including AAV-cTnT-Cre in the heart and AAV-CMV-Cre in the brain.Conclusions:To our knowledge,this work represents the first successful establish-ment of a conditional knockout model in the golden Syrian hamster,providing a valu-able tool for mechanistic studies of gene function and disease modeling.